Integrated circuit fabrication system with adjustable gas injector

ABSTRACT

The present disclosure provides a semiconductor fabrication apparatus. The semiconductor apparatus includes a processing chamber; a substrate stage provided in the processing chamber and being configured to secure and rotate a semiconductor wafer; a gas injector configured to inject a chemical to the processing chamber; a window attached to the gas injector; and an adjustable fastening device coupled with the gas injector and the window.

PRIORITY DATA

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/565,325 filed Sep. 29, 2017, the entire disclosure of whichis hereby incorporated herein by reference.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component or line that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofprocessing and manufacturing ICs and, for these advances to be realized,similar developments in IC processing and manufacturing equipment areneeded. In one example, a plasma processing system is utilized toperform plasma etching process. During a plasma etching process, theplasma generates volatile etch products from the chemical reactionsbetween the elements of the material etched and the reactive speciesgenerated by the plasma, which modifies the surface of the target. Theplasma processing system includes a processing chamber maintained atvacuum state and a chemical supply module to provide chemical tochemical for etching. However, the chemical supply module in theexisting IC fabrication system experience leaking issue, which furtherdegrades the etching performance. Accordingly, it would be desirable toprovide a IC fabrication system and a method utilizing the same absentthe disadvantages discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 illustrates a schematic view of a plasma module for integratedcircuit fabrication, constructed in accordance with some embodiments.

FIG. 2 illustrates a schematic view of the plasma module having a gasinjector with an adjustable fastening mechanism, constructed inaccordance with some embodiments.

FIG. 3A illustrates a schematic view of the adjustable fastening device,constructed in accordance with some embodiments.

FIG. 3B illustrates a top view of the adjustable fastening device inportion, constructed in accordance with some embodiments.

FIG. 4 illustrates a top view of an injector tip of the gas injector,constructed in accordance with some embodiments.

FIG. 5 illustrates a schematic view of an integrated circuit (IC)fabrication system having the plasma module, constructed in accordancewith some embodiments.

FIG. 6 is a flowchart of a method to utilize the plasma module, inaccordance with some embodiments.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Moreover, the formation of a first feature over or on a second featurein the description that follows may include embodiments in which thefirst and second features are formed in direct contact, and may alsoinclude embodiments in which additional features may be formedinterposing the first and second features, such that the first andsecond features may not be in direct contact.

FIG. 1 illustrates a schematic view of a plasma module 100 forintegrated circuit (IC) fabrication, constructed in accordance with someembodiments. With reference to FIG. 1 and other figures, the plasmamodule 100 and the method utilizing the same are collectively describedbelow.

The plasma module 100 includes a processing chamber 102 with enclosedspace 104 for semiconductor processing. In the present embodiment, thesemiconductor processing is plasma etching, such as plasma etching tometal or poly-silicon. The processing chamber 102 includes various wallsintegrated together such that the enclosed space 104 is isolated fromthe environment and can be maintained at a suitable state, such asvacuum or a low pressure.

The plasma module 100 also includes a substrate stage 106 provided inthe processing chamber 102 to secure a semiconductor substrate 108, suchas a silicon wafer. The substrate stage 106 is designed with a rotationmechanism 110, such as a motor. The substrate stage 106 is operable torotate by the rotation mechanism 110 around a rotation axis 112 so thatthe semiconductor substrate 108 secured on the substrate stage 106rotates as well during an IC fabrication.

The plasma module 100 includes one or more chemical delivery unit 114integrated to the processing chamber 102 and is designed to provide achemical to the processing chamber 102. In various examples, thechemical is an etching gas or a carry gas, such as nitrogen, argon orother suitable gas. The chemical delivery unit 114 includes anadjustable gas injector 116 attached to the processing chamber anddesigned to inject the chemical into the processing chamber 102. Thechemical delivery unit 114 is further connected to a chemical supplysource 118 to provide the chemical to the gas injector 116. The chemicaldelivery unit 114 is further described in details later.

The plasma module 100 may further includes components, modules and partsintegrated together to be functional for IC fabrication, such as plasmaetching. For example, the plasma module 100 includes a pumping module120 integrated with the processing chamber 102 and being operable tomaintain the space 104 inside the processing chamber 102 at vacuum stateor a low pressure. In various examples, the pumping module 120 mayinclude one or more pumps, and may utilize multiple pumpingtechnologies, such as positive displacement pump, momentum transferpump, regenerative pump or entrapment pump. Various pumps may beconfigured in series according to respective working ranges.

The plasma module 100 includes a plasma generation module 122 togenerate plasma inside the space 104 in the processing chamber 102. Theplasma generation module 122 introduces energy power into the processingchamber to ignite plasma with any suitable technology, such ascapacitive-coupled plasma or inductive-coupled plasma.

FIG. 2 illustrates a schematic view of the plasma module 100, inportion, constructed in accordance with some embodiments. The chemicaldelivery unit 114 is illustrated with more details. Particularly, thechemical delivery unit 114 includes an adjustable fastening mechanism.The chemical delivery unit 114 includes a fixture 202 to attach andsecure the gas injector 116 onto the top cover 204 of the processingchamber 102. The gas injector 116 includes a cylindrical body 206 toprovide a passage for the chemical to a gas injector head 208 configuredon one end of the cylindrical body 206. The chemical is delivered to thegas injector 116 from the chemical supply source 118 through an inlet210 that connects the chemical supply source 118 to the gas injector116.

The gas injector 116 further includes an O-ring 212 disposed on the gasinjector 116, such as on a circular groove of the gas injector 116; atransparent window 214 configured on the O-ring 212; and a gas injectorcover 216 configured on the transparent window 214, which is aligned tothe center 218 of the gas injector cover 216. When the above threecomponents are held together, they provide a sealing effect such thatleakage is eliminated. Furthermore, the transparent window 214 providesan additional function, such as monitoring the IC fabrication inside theprocessing chamber, or particularly monitoring the plasma signal in theplasma module 100. The transparent window 214 is made of a materialtransparent to detection signal or visual light. In the presentembodiment, the transparent window 214 is made of liquid silicone rubber(LSR). The transparent window 214 is designed with a suitable shape,such as a round plate.

The gas injector cover 216 is designed to cover the cylindrical body 206and may be made of a suitable material with enough mechanical strengthand meeting other requirements. For examples, the gas injector cover 216is made of polytetrafluoroethylene (PTFE). In the present embodiment,the top surface of the gas injector cover 216 is an inclined plane bydesign.

The chemical delivery unit 114 further includes an adjustable fasteningdevice (AFD) 220 to hold the gas injector cover 216, the transparentwindow 214 and the O-ring 212 together with adjustable height forenhanced sealing effect. In some embodiments, the gas injector 116includes an extension portion 222. The adjustable fastening device 220hold the gas injector cover 216, the transparent window 214, the O-ring212, and the gas injector together through the extension portion 222.

FIG. 3A illustrates a schematic view of the adjustable fastening device220, constructed in accordance with some embodiments. The adjustablefastening device 220 is further described in details. The AFD 220includes a base plate 302 disposed on the gas injector cover 216. Thebase plate 302 is designed to have suitable geometry to enable thefastening effect between the gas injector cover 216 and the base plate302 and to have a suitable material, such as PTFE, for the mechanicalstrength and other functions. With AFD 220, the gas injector 116 isadjustable for height, distance, fastening force and sealing effect.

In the present embodiment, the base plate 302 includes a top portion302A and a bottom portion 302B having different sizes. As illustrated inFIG. 3A, the top portion 302A spans a dimension D1 and the bottomportion 302B spans a dimension D2 less than D1.

The AFD 220 includes multiple sets of bolt and nuts, each set beingreferred to as a fastener 304. In the present embodiment, the number ofthe fasteners is three. Each fastener 304 includes a bolt 306 with abolt head 308 designed to a structure, such as groove or socket, toprovide a means for driving or holding the bolt. Each fastener 304further includes a first nut 310 and a second nut 312 sleeved on thecorresponding bolt 306. Each bolt has a thread pattern on the insidesurface and each nut has an opening with thread pattern on insidesurface. The nuts and bolt are configured for fastening by threadfriction. The first nut 310 is configured above the base plate(particularly, between the bolt head 308 and the base plate 302); andthe second nut 312 is configured between the base plate 302 and the gasinjector cover 216. The first nut 310 is operable to control the heightof the gas injector cover 216 or control the distance between the baseplate 302 and the gas injector cover 216; and the second nut 312 isoperable to fasten the gas injector cover 216 to the gas injector 220,such as the extended portion 222 of the gas injector 116 configuredbetween the base plate 302 and the gas injector cover 216.

Furthermore, the base plate 302, the gas injector cover 216 and the gasinjector 116 (or the extension portion 222 of the gas injector in thepresent case) each have a plurality of thread holes equidistantlydistributed in a way so the plurality of bolts 306 are able to passthrough the corresponding thread holes and are tightened to hold thosecomponents together. For example, FIG. 3B illustrates a top view of thebase plate 302 with three thread holes 316. The three thread holes 316are equidistantly distributed on the base plate 302, such as on a circle318. In the present examples, the top portion 302A and the bottomportion 302B have round shapes. The thread holes 316 are formed on theedge region of the top portion 302A outside of the bottom portion 302B.

Thread holes on the gas injector cover 216 and the extension portion 222are similarly configured. The thread holes match the thread pattern ofthe blots. When the fasteners 304 are configured as described above,each of the first nuts 306 is tuned to control the height of the gasinjector 116, or the distance between the gas injector cover 216 and theextension portion 222 of the gas injector 116 at corresponding location;and the second nut 308 is fastened to hold the gas injector cover 216and the gas injector 116 together.

In the existing structure, the fasteners are designed without thisadjustment mechanism, the uneven fastening forces among differentfasteners and the distortion caused thereby cannot be effectivelyadjusted and eliminated, thus causing the uneven contacts and forcesbetween the transparent window 214 and the O-ring 212. This furtherleads to leaking issue through the interface between the transparentwindow 214 and the O-ring 212. In the disclosed AFD 220, each fastener304 independently and individually can be tuned with correspondingheight and distance at the corresponding location to achieve theoptimized sealing effect between the O-ring 212 and the transparentwindow 214, thereby the leakage being eliminated.

FIG. 4 illustrates a top view of the gas injector head 208 in accordancewith some embodiments. The gas injector head 208 includes a plurality ofopenings for the chemical gas to be injected therethrough. In thepresent embodiment, the gas injector head 208 includes a central opening402 and multiple edge openings 404 equidistantly distributed on theedge. For examples, the gas injector head 208 includes eight edgeopenings 404. The edge openings 404 have a smaller radius than that ofthe central opening 402.

FIG. 5 is a block diagram of an integrated circuit (IC) fabricationsystem 500 in accordance with some embodiments. The IC fabricationsystem 500 includes one or more plasma modules 100 integrated togetherin in a cluster tool. Especially, the plasma module 100 includes one ormore chemical delivery unit 114 each having an AFD 220 to fasten the gasinjector cover 216 and provide enhanced sealing effect to the interfacebetween the transparent window 214 and the O-ring 212. In anillustrative embodiment, the IC fabrication system 500 includes twoplasma module 100 properly configured and integrated.

The IC fabrication system 500 includes one or more load port 502,through which wafers are loaded and unloaded to the IC fabricationsystem 500. In the present embodiments, the wafers are loaded andunloaded in batches, by using wafer containers, such as front openingunified pods (FOUPs).

The IC fabrication system 500 may include a loader (or front end unit)504 for holding, manipulating and transferring wafers. For examples, theloader 504 includes one or more substrate stage 506 for holding and/ororienting one or more wafer. In other examples, the loader 504 includesone or more robot 508 for handling wafers, such as transferring wafersto the plasma modules 100 or to load lock chambers (or load lock units)510. The robot 508 is configured between the load port 502 and the loadlock chambers in a way for proper wafer transferring therebetween. Forexample, each wafer is transferred by the robot 508 from the load port502 or from the substrate stage 506 to one of load lock chambers, or istransferred back to the load port 502 by the robot 508. In someembodiments, the IC fabrication system 500 may further include othercomponents, such as one or more load lock chambers 510 configured anddesigned for various functions, such as pre-orientation andpreconditioning. The preconditioning may include degassing, pre-heatingor other functions. For examples, multiple load lock chambers 510 maydesigned and configured for various preconditioning functions,respectively. In some examples, a wafer is oriented, degassed and/orpre-heated in one of the load lock chambers 510 to prepare the wafer forthe plasma processing. The IC fabrication system 500 may be configureddifferently. For example, the load lock chamber 510 in the middle may beused as a path to transfer the wafer(s). In other examples, the ICfabrication system 500 may further include a vacuum module integrated toprovide vacuum conditions to respective regions, such as the plasmamodules 100. The load ports 502, the loader 504 and the load lockchambers 510 are collectively referred to as a load lock module 512.

The IC fabrication system 500 may further include a transfer module 514for wafer transfer between the plasma modules 100 and the load lockchambers 510. In some embodiments, the transfer module 514 furtherincludes one or more robot 516 for wafer transferring. The transfermodule 514 has openings (doors) 518 connected to the plasma modules 100,respectively.

FIG. 6 is a flowchart of a method 600 fabricating one or moresemiconductor wafers 108 ((particularly, plasma etching a material layerof the semiconductor wafer), in accordance with some embodiments. Themethod 600 is implemented in the IC fabrication system 500 of FIG. 5 .The method 600 is described with reference to FIGS. 5, 6 and otherfigures.

The method 600 includes an operation 602 to fasten the gas injector 116with the AFD 220. As noted above, the AFD 220 includes multiple sets offasteners 304, each further including a bolt 306 and two nuts 310 and312 sleeved on the corresponding bolt 306. The first nut 310 isconfigured above the base plate (particularly, between the bolt head 308and the base plate 302); and the second nut 312 is configured betweenthe base plate 302 and the gas injector cover 216. The operation 602 mayinclude multiple steps. For examples, the operation 602 includes a step604 to dispose the base plate 302 on the gas injector cover 216 in aproper configuration such that the thread holes of the both parts arealigned.

The operation 602 also includes a step 606 to configure the fasteners304 with the base plate 302 and the gas injector cover 216. In thepresent embodiment, the AFD 220 includes three sets of fasteners 304. Toeach fastener 304, the first nut 310 and the second nut 312 are sleevedon the corresponding bolt 306. Particularly, the first nut 310 isconfigured above the base plate (particularly, between the bolt head 308and the base plate 302); and the second nut 312 is configured betweenthe base plate 302 and the gas injector cover 216.

The operation 602 includes a step 608 to adjust the height of the gasinjector cover 216 (or control the distance between the base plate 302and the gas injector cover 216) by tuning the first nut 310; and a step610 to fasten the gas injector cover 216 to the gas injector 220 bytuning the second nut 312, which adjusts a fastening force between thegas injector cover and the gas injector and further the contact forcebetween the O-ring 212 and the transparent window 214.

The steps 608 and 610 are repeated to other fasteners 304 and may repeatmany cycles to all fasteners until the gas injector cover 216 isfastened to the gas injector 116 such that the O-ring 214 and thetransparent window 214 are evenly contacted with improved sealingeffect, thereby eliminating leaking through the interface between thatthe O-ring 214 and the transparent window 214.

After the completion of the operation 602 and other initialconditioning, the IC fabrication system 500 is ready for and may proceedto IC fabrication. For example, the method 600 may include an operation614 to load one or more wafers to the IC fabrication system 500 throughthe load ports 502. For example, wafers are in one or more batches, suchas in FOUPs, are loaded to the IC fabrication system 500 through theload ports 502 in one or more steps, such as loading, degassing,pre-heating, orienting or a subset thereof.

The method 600 includes operation 614 to transfer one or more wafer toone of the plasma module 100 by the robot 516 through the opening 518.For example, the robot 516 sequentially transfers one or more wafer toeach of the plasma modules 100. In other examples, the transfer module514 may include two or more robots 516 to simultaneously transfer wafersto respective plasma modules 100. Specifically, in the presentembodiment, one wafer 108 is transferred to the substrate stage 106 ofthe corresponding plasma module 100 in a configuration that the frontsurface of the wafer faces upward.

The method 600 proceeds to an operation 616 to perform plasma process tothe wafer(s) 108 in one of the plasma modules 100. The operation 616 andfollowing operations are described with one plasma module and one wafer.However, as described above, the multiple wafers may be processed in oneof multiple plasma modules 100 and the multiple plasma modules 100 maywork in parallel. In the present embodiment, a plasma process is aplasma etching process being applied to the front surface of the wafer108 during the operation 516. For example, one or more chemicaldelivered to the processing chamber 102 may be partially converted intoplasma to provide etching effect to the semiconductor wafer 108. In someembodiments, the operation 616 may include injecting the chemical to theprocessing chamber 102 by the gas injector 116; generating plasma to thechemical; and directing the chemical to the semiconductor wafer 108 foretching.

In one example, the front surface of the wafer 108 includes a metallayer, and the plasma etching process is applied to selectively etch themetal. In furtherance of the example, the metal is copper, the etchant(etching gas) may include CH₄ and Ar; CH₄ and N₂; H₂ and Ar; or H₂ andN₂. Accordingly, each plasma module 100 may include more than chemicaldelivery unit 114 to deliver the corresponding gases.

In one example, the front surface of the wafer 108 includes apoly-silicon layer, and the plasma etching process is applied toselectively etch the poly-silicon. In furtherance of the example, theetchant include HBr, Cl₂, SF₆, O₂, Ar, He, or a combination thereof.Accordingly, each plasma module 100 may include more than chemicaldelivery unit 114 to deliver the corresponding gases.

In yet another example, the front surface of the wafer 108 includes asilicon oxide layer, and the plasma etching process is applied toselectively etch the silicon oxide. The etchant may include CF₄, C₃F₈,C₄F₈, CHF₃, CH₂F₂ or a combination thereof. The plasma process may be,alternatively, plasma-enhanced deposition or plasma treatment.

After the completion of the deposition process to the wafer 108 in theplasma modules 100 by the operation 616, the method 600 proceeds to anoperation 618 to transfer the wafer 108 to the load lock chamber(s) 510by the robot 516. This operation is similar to the operation 614 but itis reversed. For example, the multiple wafers are transferred to theload lock chambers 510 from the plasma modules 100, sequentially or inparallel by multiple robots 516.

The method 600 may further include an operation 620 to unload the wafersfrom the IC fabrication system 500 through the load port 502. The method600 may include other operations, before, during or after the operationsdescribed above. For example, after the operation 620, the wafers may betransferred to other fabrication tools for following fabrications, suchas lithography patterning process.

The IC fabrication system 500 and the method 600 may have otherembodiments, or alternatives. For examples, even though the method 600describes a procedure to perform a plasma etch to a wafer, the ICfabrication system and the method utilizing the same may be used to formvarious thin films, such as etching a gate dielectric layer, a gateelectrode layer, a capping layer, a barrier layer, an etch stop layer, adielectric layer for interlayer dielectric, or a conductive layer formetal lines.

The present disclosure provides an IC fabrication system and a methodutilizing the same. By utilizing the disclosed IC fabrication system,the plasma process, such as plasma etching quality and efficiency areimproved. The IC fabrication system includes one or more plasma module100, each further including one or more chemical delivery unit 114 withan AFD 220. The AFD 220 includes multiple sets of fasteners 304, eachfurther including a bolt 306 and two nuts 310 and 312 sleeved on thecorresponding bolt 306. The first nut 310 is configured above the baseplate (particularly, between the bolt head 308 and the base plate 302);and the second nut 312 is configured between the base plate 302 and thegas injector cover 216. The first nut 310 is tuned to control thedistance and the second nut 312 is tuned to provide fastening force tosecure the gas injector cover 216 to the gas injector 116 in a way suchthat the O-ring 214 and the transparent window 214 are evenly contactedwith improved sealing effect, thereby eliminating leaking through theinterface between that the O-ring 214 and the transparent window 214.

The embodiments of the present disclosure offer advantages over existingart, though it is understood that other embodiments may offer differentadvantages, not all advantages are necessarily discussed herein, andthat no particular advantage is required for all embodiments. Variousadvantages may present in some embodiments. By utilizing the disclosedIC fabrication system and the method, the IC fabrication, such as plasmaetching, is improved with enhanced sealing and fabrication efficiency.Other advantages may include less manufacturing cost and highermanufacturing throughput.

Thus, the present disclosure provides a semiconductor fabricationapparatus. The semiconductor fabrication apparatus includes a processingchamber; a substrate stage provided in the processing chamber and beingconfigured to secure and rotate a semiconductor wafer; a gas injectorconfigured to inject a chemical to the processing chamber; a windowattached to the gas injector; and an adjustable fastening device coupledwith the gas injector and the window.

The present disclosure provides a semiconductor fabrication apparatus.The semiconductor fabrication apparatus includes a processing chamber; asubstrate stage configured in the processing chamber and being operableto secure and rotate a semiconductor wafer; a gas injector attached tothe processing chamber and designed to inject a chemical to theprocessing chamber; an O-ring configured to the gas injector; a windowattached to the gas injector and in direct contacting with the O-ring; agas injector cover disposed on the window; and an adjustable fasteningdevice integrated with the gas injector and designed to secure thewindow and the gas injector cover to the gas injector with an adjustableheight.

The present disclosure provides a method for semiconductor fabrication.The method includes providing a semiconductor fabrication apparatus. Thesemiconductor fabrication apparatus further includes a processingchamber; a substrate stage configured in the processing chamber andbeing operable to secure and rotate a semiconductor wafer; a gasinjector attached to the processing chamber and designed to inject achemical to the processing chamber; an O-ring configured to the gasinjector; a window attached to the gas injector and in direct contactingwith the O-ring; a gas injector cover disposed on the window; and anadjustable fastening device integrated with the gas injector anddesigned to secure the window and the gas injector cover to the gasinjector with an adjustable height. The adjustable fastening deviceincludes a base plate configured on the gas injector cover; and aplurality of fasteners to fasten the gas injector cover to the gasinjector, wherein each of the fasteners includes a bolt, a first nut anda second nut both sleeved on the bolt, wherein the first nut isconfigured above the base plate and the second nut is configured betweenthe base plate and the gas injector cover. The method further includesperforming an etching process to the semiconductor wafer by thesemiconductor apparatus.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor fabrication apparatus,comprising: a processing chamber; a substrate stage provided in theprocessing chamber and being configured to secure and rotate asemiconductor wafer; a gas injector configured to inject a chemical tothe processing chamber, wherein the gas injector comprises a cylindricalbody having a passage, the cylindrical body includes a lower portionsecured to the processing chamber and an upper portion on the lowerportion, wherein the gas injector further comprises an extension portionadjacent to the upper portion of the gas injector and one or more inletsdisposed on a sidewall of the upper portion of the cylindrical body,wherein the one or more inlets are configured to receive the chemicalfrom a gas supply source and deliver the chemical to the passage; atransparent window disposed over the cylindrical body of the gasinjector; an O-ring interposed between the gas injector and thetransparent window, wherein the 0-ring directly contacts the gasinjector and the transparent window; a gas injector cover disposed onboth the gas injector and the transparent window, wherein a bottomsurface of the gas injector cover is in direct contact with top surfacesof the transparent window and the extension portion of the gas injector,the top surface of the extension portion of the gas injector is above atop surface of the cylindrical body of the gas injector, and the gasinjector cover is spaced apart from the cylindrical body of the gasinjector by the transparent window; and an adjustable fastening devicedisposed over the gas injector cover and configured to hold thetransparent window, the O-ring and the gas injector cover together toprovide a sealing effect, wherein the adjustable fastening devicecomprises a base plate disposed over the gas injector cover.
 2. Thesemiconductor fabrication apparatus of claim 1, wherein the O-ring isdisposed on a circular groove of the gas injector and is capped by thetransparent window.
 3. The semiconductor fabrication apparatus of claim2, wherein the transparent window is made of liquid silicon rubber. 4.The semiconductor fabrication apparatus of claim 2, wherein theadjustable fastening device further includes a plurality of fastenersconfigured to fasten the gas injector cover to the gas injector.
 5. Thesemiconductor fabrication apparatus of claim 4, wherein the gas injectorcover has an inclined top plane and the base plate is configured todirectly contact the inclined top plane of the gas injector cover. 6.The semiconductor fabrication apparatus of claim 5, wherein each of thefasteners includes a bolt having a bolt head, a first nut and a secondnut both sleeved on the bolt and disposed under the bolt head, whereinthe base plate includes a top portion having a first dimension D1 and abottom portion having a second dimension D2 less than D1, wherein thefirst nut is in direct contact with a top surface of the top portion ofthe base plate and disposed between the bolt head and the base plate,and the second nut is configured below a bottom surface of the topportion of the base plate and is interposed between the base plate andthe gas injector cover, wherein the second nut is in direct contact withthe gas injector cover, and the bolt extends through the top portion ofthe base plate.
 7. The semiconductor fabrication apparatus of claim 6,wherein the first nut is operable to adjust a distance between the gasinjector cover and the base plate; and the second nut is operable toadjust a fastening force between the gas injector cover and the gasinjector.
 8. The semiconductor fabrication apparatus of claim 6, whereinthe gas injector cover includes a plurality of cover thread holesequidistantly distributed in a circle around a center of the gasinjector cover; the base plate includes a plurality of base thread holesequidistantly distributed in a circle around a center of the base plate;and the plurality of fasteners are configured with respective bolts eachpassing through one of the base thread holes and one of the cover threadholes.
 9. The semiconductor fabrication apparatus of claim 8, whereinthe plurality of cover thread holes includes three cover thread holes;the plurality of base thread holes includes three base thread holes; andthe plurality of fasteners includes three fasteners.
 10. Thesemiconductor fabrication apparatus of claim 1, wherein the gas injectorcover is made of polytetrafluoroethylene (PTFE).
 11. The semiconductorfabrication apparatus of claim 1, further comprising: a pump moduleintegrated to the processing chamber and configured to control apressure thereof; and a plasma generating module integrated with theprocessing chamber and configured to generate plasma therein, whereinthe chemical is injected into the processing chamber by the gas injectorand is further converted into plasma to provide etching effect to thesemiconductor wafer.
 12. A semiconductor fabrication apparatus,comprising: a processing chamber; a substrate stage configured in theprocessing chamber and being operable to secure and rotate asemiconductor wafer; a gas injector comprising an inlet, a cylindricalbody having a passage, and an extension portion adjacent to an upperportion of the cylindrical body, wherein the upper portion of thecylindrical body is mechanically coupled to the inlet which isconfigured to receive a chemical from a chemical supply source, and alower portion of the cylindrical body is mechanically coupled to theprocessing chamber and configured to inject the chemical to theprocessing chamber through the passage, wherein the extension portion ofthe gas injector comprises a plurality of first thread holes; an O-ringprovided in a circular groove of the gas injector; a transparent windowdisposed on the cylindrical body of the gas injector and in directcontact with the O-ring; a gas injector cover disposed on thetransparent window and the gas injector and comprising a plurality ofsecond thread holes, wherein a bottom surface of the gas injector coveris in direct contact with both the transparent window and the extensionportion of the gas injector, and wherein the gas injector cover isspaced apart from the cylindrical body of the gas injector; and anadjustable fastening device mechanically coupled to the extensionportion of the gas injector, wherein the adjustable fastening devicecomprises a base plate and a plurality of fasteners, wherein the baseplate is disposed over the gas injector cover and includes a pluralityof third thread holes, the plurality of fasteners are engaged with theplurality of first, second, and third thread holes to secure thetransparent window and the gas injector cover to the extension portionof the gas injector.
 13. The semiconductor fabrication apparatus ofclaim 12, wherein each of the plurality of fasteners includes a threadedbolt having a bolt head, a first nut and a second nut both sleeved onthe threaded bolt and disposed under the bolt head.
 14. Thesemiconductor fabrication apparatus of claim 13, wherein the base plateincludes a top portion having a first dimension D1 and a bottom portionhaving a second dimension D2 less than D1; the first nut is disposedbetween the base plate and the bolt head and in direct contact with thebase plate; and the second nut is configured below the top portion ofthe base plate and above the gas injector cover and in direct contactwith the gas injector cover.
 15. The semiconductor fabrication apparatusof claim 14, wherein the first nut is operable to adjust a distancebetween the gas injector cover and the base plate; and the second nut isoperable to adjust a fastening force between the gas injector cover andthe gas injector.
 16. The semiconductor fabrication apparatus of claim15, wherein the plurality of second thread holes include three threadholes and are equidistantly distributed in a circle around a center ofthe gas injector cover; the plurality of third thread holes includethree thread holes and are equidistantly distributed in a circle arounda center of the base plate; and the plurality of fasteners areconfigured such that each bolt passing through one of the plurality ofthird thread holes and one of the plurality of second thread holes. 17.The semiconductor fabrication apparatus of claim 12, further comprising:a pump module integrated to the processing chamber and configured tocontrol a pressure thereof; and a plasma generating module integratedwith the processing chamber and configured to generate plasma therein,wherein the chemical is injected into the processing chamber by the gasinjector and is further converted into plasma to provide etching effectto the semiconductor wafer.
 18. A semiconductor fabrication apparatus,comprising: a processing chamber; a substrate stage configured in theprocessing chamber and being operable to secure and rotate asemiconductor wafer; a gas injector comprising a cylindrical body havingan upper portion and a lower portion and designed to inject a chemicalto the processing chamber, wherein the upper portion is configured toreceive a chemical via an inlet disposed thereon, and the lower portionis mechanically coupled to the processing chamber, wherein the gasinjector further comprises an extension portion adjacent to the upperportion; a transparent window disposed on the upper portion of thecylindrical body of the gas injector; an O-ring disposed on a circulargroove of the upper portion of the cylindrical body of the gas injectorand capped by the transparent window, wherein the O-ring directlycontacts the gas injector and the transparent window; a gas injectorcover disposed above both the gas injector and the transparent window,and wherein the gas injector cover is in direct contact with topsurfaces of the extension portion of the gas injector and thetransparent window and is spaced apart from the cylindrical body of thegas injector; and an adjustable fastening device mechanically coupled tothe gas injector and designed to secure the transparent window and thegas injector cover to the gas injector, wherein the adjustable fasteningdevice comprises: a base plate disposed over the gas injector cover,wherein the base plate is an integral structure and comprises a topportion having a first dimension D1 and a bottom portion having a seconddimension D2, D2 is less than D1, wherein the top portion is spacedapart from the gas injector cover by the bottom portion; and a pluralityof fasteners configured to fasten the gas injector cover to the gasinjector, wherein each of the plurality of fasteners comprises acorresponding bolt having a bolt head, a first corresponding nut and asecond corresponding nut both sleeved on the corresponding bolt anddisposed under the bolt head, wherein the first corresponding nut ispositioned between the top portion of the base plate and the gasinjector cover and in direct contact with the gas injector cover tooperably adjust a fastening force between the gas injector cover and thegas injector, and wherein the second corresponding nut is positionedbetween the bolt head and the top portion of the base plate and indirect contact with the top portion of the base plate to adjust adistance between the base plate and the gas injector cover.
 19. Thesemiconductor fabrication apparatus of claim 18, wherein the gasinjector cover has an inclined top surface in direct contact with abottom surface of the base plate.
 20. The semiconductor fabricationapparatus of claim 18, wherein the second dimension D2 is less than D1such that the corresponding bolt passes through a first correspondingthread hole in the top portion and a second corresponding thread hole inthe gas injector cover without passing through the bottom portion.